1. Fields of the Invention
The present invention relates to an injection drive apparatus for injection molding machines, especially to a driving mechanism for injection molding machines that reduces load of a motor and increases the yield rate of the injection molding products by two-stage action—initially feeding liquid plastic material into a mold smoothly and then squeezing the material for injection molding.
2. Descriptions of Related Art
As to servo injection molding machines available now, as shown in U.S. Pat. No. 5,129,808, a motor is used to drive two ball screws for further driving a rear end face, a metering motor, and related parts. The driving member includes a plurality of linear guides and guide bars that are difficult to maintain parallel to one another, move synchronously and control the precision. Moreover, due to heavier weight, the energy consumption for driving is large.
Moreover, refer to U.S. Pat. No. 4,693,676, an injection motor is used to rotate ball screws for moving a pressure plate and a screw shaft forward. And a servo motor is used to rotate the screw shaft.
Furthermore, refer to Taiwanese Pat. App. No. M270033, an injection drive apparatus for servo injection molding machines includes a barrel base, an injection base and a material feeding base, arranged with a certain interval therebetween. A barrel with a feeding screw is inserted and mounted in the barrel base and a ball screw with ball nuts and peripheral disc is inserted and disposed on the injection base and is driven by an injection motor. One end of the ball screw is connected with the feeding screw to form an axis line while the other end thereof is with a central channel with a spline nut. A spline shaft with a disc is inserted and located on the material feeding base and is driven by a material-feeding motor. One end of the spline shaft is slidingly joined with the spline nut of the ball screw so as to make the spline shaft only rotate, without axial displacement along with the ball screw. Thus the inertia (inertial force) is reduced.
Due to complicated design of the injection drive apparatus of the servo injection molding machines, there is a need to develop a new injection drive apparatus for injection molding machines.